# What is the chemical formula of calcium hydroxide?

Calcium hydroxide is formed by one $C {a}^{2 +}$ cation and two $O {H}^{-}$ anions, which implies that its chemical formula will be $C a {\left(O H\right)}_{2}$.
On the other hand, oxygen is in group 6, which means it needs 2 electrons in order to be stable. It gets one electron from a hydrogen atom to form an $O {H}^{-}$ anion. Now it only needs one more electron, which it gets from the two calcium has to offer.
This means that you'd need two $O {H}^{-}$ groups to form calcium hydroxide, since each $O {H}^{-}$ group would get one electron from calcium $\to$ $C a {\left(O H\right)}_{2}$.